O2 sensor codes—could it be a bad ground or PCM issue?

[GreenMountanTJ]

I posted about this a little while back but my o2 sensors keep giving me codes (P0174, P0157, P0031, P0037, P0051, P0057, P0157) These are for bank 1/2 lean and bad heaters. I thought the culprit was that I had replaced them with bosch ones in the spring, but I checked them and it turns out i did use the correct NTK ones after all. I then read that it can be a bad block ground (ground wire 105) so I checked and cleaned it and it seemed ok, but i'm not sure if i did this right as the light came back on. Has anyone else had this bad ground issue causing o2 sensor codes? I'm not sure how extensively to clean it, or what causes this connector to get corroded. Also, what other issues can cause this code? My jeep is an 05 automatic ,and i've heard alot of them have pcm issues. I've also heard to check the harness, but before I do, has anyone actually had a harness go bad? If so, where was the break/bad connection? Any other ideas on what could be causing the issue? If anyone has an answer to any of these questions it would be a huge help!

 

[CharlesHS]

Do a search on the Forum; IF I remember correctly there is a Technical Service Bulletin that addresses similar problems for 05/06 TJs.
There is a wiring modification outlined in the TSB that should cure some of these problems.

 

[AjRagno]

TSB SB 25-001-07 is for '05-'06 emissions testing readiness. That was simply an OBD communication failure issue during emissions testing, it won't address the 02 sensor heater circuit.

You may have mechanical issues, like an exhaust leak or low fuel pressure, setting some of these codes. But every time I see all 4 codes for the 02 sensor heaters at once it's been a PCM issue.

 

[AndyG]

@Wranglerfix will shoot straight with you.

 

[CharlesHS]

Before throwing money and parts at the problem; spend a few minutes and check the (3) 32 pin harness connectors for the ECM. Verify the harness clips and pins for the ECM are clean (no oxidation) and then ensure the harness connectors are snapped into the ECM harness ports. IF the ECM can not receive the signals or transmit the signals the engine will not run properly.

 

[L J]

I had the 31, 37, 51, 57 codes. I swapped in new NTKs to no avail. A retired CDJ mechanic troubleshot it with his DRB and it turned out the PCM was junk.

 

[Wranglerfix]

@GreenMountanTJ Are you experiencing any other symptoms? High transmission temperatures, hard shift from 1st to 2nd when cold?

Spray your connectors with contact cleaner and inspect for bent pins or corrosion.

Do not use dielectric grease as over time it cakes up causing connectivity issues.

 

[GreenMountanTJ]

@GreenMountanTJ Are you experiencing any other symptoms? High transmission temperatures, hard shift from 1st to 2nd when cold?

Spray your connectors with contact cleaner and inspect for bent pins or corrosion.

Do not use dielectric grease as over time it cakes up causing connectivity issues.

I checked the connectors at the sensors and at the pcm and they both appear to be clean and in good shape. There does appear to be a small amount of dielectric grease on the pcm pins already though, do you think this could this be causing any issues? Also yes, my transmission shifts hard occasionally but I usually attribute that to it having a leak for most of the summer and probably having too much or too little fluid in it rn.

 

[CharlesHS]

While dielectric grease is good for certain applications; you should not apply it to the (3) 32 pin connectors for the PCM. Disconnect the vehicles battery, wipe the pins and connector with a rag and then spray plastic safe contact cleaner (this can be purchased at Walmart) on the harness connector and the PCM pins. Allow the contact cleaner to aerate for a couple minutes to ensure it's fully evaporated.
As for the transmission fluid level; you should make sure the fluid level is at the recommended amount.

 

[Jerry Bransford]

My 04's repetitive O2 codes and occasional misfires were caused by a bad pre-catalytic converter. The cats were replaced 7-8 years ago and no more O2 codes. The old O2 sensors were reinstalled with the new cats. And of course it could be a bad PCM too.

 

[GreenMountanTJ]

My 04's repetitive O2 codes and occasional misfires were caused by a bad pre-catalytic converter. The cats were replaced 7-8 years ago and no more O2 codes. The old O2 sensors were reinstalled with the new cats. And of course it could be a bad PCM too.

I'm pretty confident its electrical and not a cat issue only because it throws all 4 heater codes immediately after I clear them. I think if was bad cats I would be getting more varied bank lean codes before the heater codes. Also, the engine runs fine so i don't think there is any clogging.

 

[Wranglerfix]

The 05-06 pcm is notorious for throwing bad o2 sensor codes. With all of the due diligence done, I am leaning towards the pcm as the culprit.

In the event it does not solve your issue I accept returns -20% for shipping and programming.

You can call me at 866-888-7710 to discuss in further detail.

Thanks,

Mark